The present invention relates to processes for conjointly producing bromine, a concentrated aqueous solution of calcium chloride, and chlorine. Further this invention relates to such processes wherein at least a portion of the produced chlorine is used in the production of bromine.
Bromine is useful in a wide range of industries. For example, bromine is used in the manufacture of brominated flame retardants such as tetrabromobisphenol, decabromodiphenylethane, decabromodiphenyloxide, and brominated polystyrenes. Bromine is also used, e.g., in the manufacture of 1,2-dibromoethane, which is used as a petrol additive, in the manufacture of compounds used in photography (e.g. silver bromide, which is the light sensitive material in film), in the manufacture of dyestuffs and drugs, in analytical laboratory in testing for unsaturation in organic compounds, as a disinfectant, and in gold extraction. Calcium chloride is also useful in numerous applications, e.g., as a drying agent, in ice and dust control, in oil well drilling, in food processing, in concrete mixtures to speed up setting, as an additive in plastics, and as a drainage aid for wastewater treatment.
One source used in production of bromine and calcium chloride is brine. Brine is an aqueous solution nearly saturated with halide salts and which is produced in several areas of the United States. Such produced brines typically contain at least sodium chloride, sodium bromide and calcium chloride. Additionally, certain processes, such as processes for producing brominated flame retardants, generate substantial quantities of hydrogen bromide as a by-product, which can be converted to bromine.
Processes for production of bromine from these and other bromide-containing solutions are well know. For example, bromine can be produced by a bromine steaming out process, such as Kubierschky's distillation method; see, e.g., Kirk-Othmer, Encyclopedia of Chemical Technology, Fourth Edition, volume 4, pages 548 through 553. Other methods for recovering bromine from bromide-containing solutions are described, e.g., in U.S. Pat. Nos. 3,181,934, 4,719,096, 4,978,518, 4,725,425, 5,158,683, and U.S. Pat. No. 5,458,781.
Substantial quantities of chlorine (Cl2) are used in Kubierschky's distillation method, and in other methods for production of bromine. Chlorine is typically produced using an electrolysis method, several of which are known to those skilled in the art. Thus-produced chlorine is wet and caustic; and containers made from costly materials are required for its transport. The chlorine can be dried, compressed and cooled for transport, which is a costly endeavor. In some cases, chlorine is produced on site and sent directly to the process for production of bromine via pipeline. While costs associated with transporting chlorine make on-site production of chlorine attractive, in any of these circumstances, the cost of providing chlorine can add significantly to the cost of producing bromine.
Processes for production of calcium chloride from brines and other sources are also well known. See, e.g., U.S. Pat. No. 4,704,265, WO 03/035550, and U.S. Pat. No. 6,524,546.
Even in view of these and other published methods for production of bromine and for production of calcium chloride, it would be commercially beneficial to have processes for conjointly producing bromine, calcium chloride and chlorine, wherein at least a portion of the produced chlorine can be used in the production of bromine.